1. Field of the Invention
The present invention relates to improved methods and compositions for preventing proppant flowback from fractures.
2. Description of the Prior Art
Hydrocarbon producing wells are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous fracturing fluid which also functions as a carrier fluid is pumped into a producing zone to be fractured at a rate and pressure such that one or more fractures are formed in the zone. Particulate solids, e.g., graded sand, for propping the fractures (commonly referred to in the art as “proppant particles”) are suspended in a portion of the fracturing fluid so that the proppant particles are deposited in the fractures when the fracturing fluid is broken. That is, a delayed viscosity breaker is included in the fracturing fluid whereby the fracturing fluid reverts to a thin fluid which is returned to the surface. The proppant particles deposited in the fractures function to prevent the fractures from closing so that conductive channels are formed through which produced hydrocarbons can readily flow.
In order to prevent the subsequent flowback of proppant particles as well as formation sand and fines with fluids produced through the fractures, the proppant particles introduced into the fractures have heretofore been coated with a hardenable resin composition which is caused to harden and consolidate the proppant particles in the fractures. However, in high temperature wells, i.e., wells having subterranean temperatures greater than about 250° F., the hardened resin composition coating on the proppant particles deteriorates and proppant particle flowback occurs. The deterioration of the resin composition coated proppant particles also takes place in wells that do not have high temperatures, but are produced at very high rates. That is, high rate production flowing through the resin composition coated proppant particle packs also causes the proppant particle packs to deteriorate and proppant flowback to occur. In both types of wells where proppant flowback occurs, formation sand and fines flow through the deteriorating proppant particle packs with produced formation fluids. The flowback of the proppant particles and formation sand and fines with the produced formation fluids is very detrimental in that it erodes metal goods, plugs piping and vessels and causes damage to valves, instruments and other production equipment.
Thus, there are needs for improved methods and compositions for preventing fracture proppant particle flowback and the production of formation sand and fines with formation fluids in high temperature and/or high production wells.